Use of Unbonded CFCC for Transverse Post-Tensioning of Side-by-Side Box-Beam Bridges

An experimental and numerical research project was developed to address the effect of the level of transverse post-tensioning (TPT) and the number of the transverse diaphragms on the performance of side-by-side box-beam bridges using unbonded carbon fiber composite cables (CFCC). The experimental program included the construction, instrumentation, and testing of one half-scaled 30° skew bridge model. The numerical program investigated the sensitivity to longitudinal cracking for a wide range of side-by-side box-beam bridges with different spans and different widths. The experimental program consisted of load distribution tests conducted during three different deck slab conditions; uncracked, cracked, and repaired stage. The transverse strain distribution tests were conducted when the bridge deck was uncracked. The cracked stage involved the initiation of longitudinal cracks above the shear-key locations while the repaired stage involved the replacement of an assumed damaged exterior beam with a new one. The distribution of the transverse strain developed at the top surface of the deck slab and the deflection across the width of the bridge were examined by varying the number of transverse diaphragms (five, four, and three) and the levels of TPT forces (20, 40, and 80 kip) at each transverse diaphragm. An ultimate load test was performed to evaluate the performance of the unbonded CFCC used for TPT during failure. Analysis of the experimental results shows that the application of TPT significantly improved load distribution among the side-by-side box-beams. Increasing the level of TPT forces generally improved the deflection response of the bridge model in all the three cases studied. Different arrangements of the TPT forces had insignificant influence on the transverse strains developed in the region between the diaphragms. From the ultimate load test results, it was noted that the TPT system coupled with the deck slab distributed the eccentric load in the transverse direction until the complete failure of the bridge model. The numerical study revealed that the influence of the live load alone is not the major cause of the longitudinal cracks. Combining the temperature gradient with the live load can lead to the development of longitudinal cracks between the adjacent beams. The adequate number of diaphragms is a function of the bridge span while the adequate TPT force level is a function of the bridge width. The developed recommendations are presented in design charts relating the number of diaphragms to the bridge span and the level of the TPT force to the bridge width. The onset of longitudinal cracks can be delayed using adequate TPT arrangements.

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• Record URL:
  https://rosap.ntl.bts.gov/view/dot/28015
• Corporate Authors:

  Lawrence Technological University

  Department of Civil Engineering, 21000 West 10 Mile Road
  Southfield, MI  United States  48075-1058

  Michigan Department of Transportation

  Construction and Technology Division, P.O. Box 30049
  Lansing, MI  United States  48909
• Authors:
  • Grace, Nabil F
  • Jensen, Elin A
  • Matsagar, Vasant A
  • Bebawy, Mena
  • Soliman, Elsam
  • Hanson, Joseph
• Publication Date: 2008-2

Language

• English

Media Info

• Media Type: Web
• Edition: Final Report
• Features: Appendices; Figures; Photos; Tables;
• Pagination: 358p

Subject/Index Terms

• TRT Terms: Box beams; Bridge decks; Bridge design; Carbon fibers; Live loads; Longitudinal cracking; Posttensioning; Transverse cracking
• Subject Areas: Bridges and other structures; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 01115183
• Record Type: Publication
• Report/Paper Numbers: Research Report RC-1509
• Files: NTL, TRIS, STATEDOT
• Created Date: Nov 25 2008 7:31AM